Estimating channel frequency responses corresponding to orthogonal frequency division multiplexed (OFDM) signals may include estimating channel frequency responses corresponding to scattered pilots within the OFDM signal, interpolating the scattered pilot channel frequency responses over multiple symbols of the OFDM signal to obtain channel frequency responses corresponding to non-pilot positions of scattered pilot frequencies, and frequency interpolating the estimated channel frequency responses corresponding to the scattered pilot frequencies of a symbol, to obtain channel frequency responses corresponding to non-scattered pilot frequencies of the symbol.
Under noisy channel conditions, such as in a digital terrestrial television broadcast environment, OFDM pilots may be impacted with additive noise. In mobile applications, pilots may also be impacted by inter-carrier interference (ICI). Such impacts may degrade a signal-to-noise ratio (SNR) of channel frequency response estimates.
For stationary applications, noise may be filtered during the initial interpolation using a relatively narrow bandwidth filter, but at relatively substantial cost in terms of memory and hardware complexity. For mobile applications, using a relatively narrow bandwidth filter in the initial interpolation may result in loss of Doppler spectrum.
For low delay spread signals, noise may be filtered during the subsequent frequency interpolation by using relatively narrowband filter. However, for single frequency networks (SFN) with large multipath delays, a narrowband filter may result in loss of multipath profile.
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